Material Testing System Having Improved Hydraulic Wedge Clips

ABSTRACT

A material testing system that uses at least one hydraulic grip is improved with cable clips that are attachable to a respective lateral side of each hydraulic grip wedge. Each cable clip has another end that extends to engage a cable(s) extending from a corresponding wedge retention spring hole. The cable(s) enable manual extension of a wedge retention spring for engagement and disengagement from the hydraulic grip wedge. The cable clip maintains the cable in a noninterfering position during operational use of the material testing system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Application Ser. No. 63/079,656 entitled “MaterialTesting System Having Improved Hydraulic Wedge Grips” filed 17 Sep.2020, the contents of which are incorporated herein by reference intheir entirety.

ORIGIN OF THE INVENTION

The invention described herein was made by employees of the UnitedStates Government and may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefore.

BACKGROUND 1. Technical Field

The present disclosure generally relates to material testing usinghydraulic grips, and more particularly to material testing systemshaving hydraulic wedge grips with retention springs.

2. Description of the Related Art

Hydraulically actuated test frames are often used to evaluate the staticand fatigue properties of materials. Two typical specimen retentionmethods are (1) pin-and-clevis and (2) hydraulic grips with wedges. Anexample of such material testing systems is MTS 810 material testingsystem by MTS Systems Corporation, Eden Prairie, Minn. When installingcertain wedges used to grip test specimens with hydraulic grips on testmachines, the cables used for installation must be left in place duringsubsequent testing. The cables are necessary for pulling the wedgeretention springs up through the bottom of the wedge, via the wedgeretention spring hole, where the end of the spring is retained by awedge spring retention screw. The loose ends of these cables, if notrestrained in some manner, can interfere with access to the testspecimen and even cause minor injuries to fingers and hands.

SUMMARY

The present innovation overcomes the foregoing problems and othershortcomings, drawbacks, and challenges of hydraulically gripping a testspecimen during material testing. While the present innovation will bedescribed in connection with certain embodiments, it will be understoodthat the invention is not limited to these embodiments. To the contrary,this invention includes all alternatives, modifications, and equivalentsas may be included within the spirit and scope of the present invention.

According to one aspect of the present innovation, a material testingsystem includes a load frame and at least one hydraulic grip fixture.The load frame includes a base positioned on a support surface. The loadframe includes a pair of vertical columns extending upwardly from thebase. The load frame includes a crosshead received for vertical movementon the pair of vertical columns. The load frame includes a pair ofhydraulic linear actuators attached between the base and the crossheadto position the crosshead. Each of the at least one hydraulic gripfixture receives one end of a test specimen and is positioned betweenand attached to one of: (i) the lower attachment fixture and thecrosshead. Each of the at least one hydraulic grip fixture includes: (i)a fixture body; (ii) a pair of hydraulic grip wedges; (iii) fourretention springs; (iv) cables; (v) spring retention bolts; and (vi)cable clips. The fixture body has a wedge recess. The pair of hydraulicgrip wedges are received in opposition within the wedge recess. Eachhydraulic grip wedge has a pair of vertical wedge retention spring holesthat are perpendicularly intersected respectively by a horizontalretention bolt hole. Four retention springs have one end attached to thefixture body and another end extending upward respectively in thevertical wedge retention spring holes. The cables are engaged to theother end respectively of each extension spring and extending out of thecorresponding hydraulic grip wedge, enabling manual extension of therespective retention spring. The at least two spring retention bolts arereceived respectively in the horizontal retention bolt holes to attachto the other end of the wedge retention spring during extension by thecorresponding cable. Four or more cable clips are respectively attachedat one end to a lateral side of one of the pair of hydraulic grip wedgesand engaged at another end to a corresponding cable to maintain thecable in a noninterfering position.

According to one aspect of the present innovation, a method includesattaching a fixture body of a hydraulic grip fixture to one of a lowerattachment fixture and a crosshead of a load frame, the crossheadreceived for vertical movement on a pair of vertical columns extendingupwardly from the base. The method includes attaching four wedgeretention springs to a recess of the fixture body. The method includespassing respective one or more cables attached to each wedge retentionspring through a corresponding vertical wedge retention spring hole inone of a pair of hydraulic grip wedges. With a respective wedgeretention spring extended in the wedge retention spring hole by manualactuation of a corresponding cable, the method includes inserting aretention spring retention bolt through a horizontal bolt hole thatintersects the vertical wedge retention spring hole. The method includesattaching one end of a cable clip respectively to each lateral side ofthe pair of hydraulic grip wedges. The method includes engaging anotherend of the cable clip to a corresponding cable to maintain the cable ina noninterfering position. The method includes engaging a test specimenbetween the pair of hydraulic grip wedges. The method includes actuatinga pair of hydraulic linear actuators attached between the base and thecrosshead to materially test the test specimen.

Additional objects, advantages, and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The description of the illustrative embodiments can be read inconjunction with the accompanying figures. It will be appreciated thatfor simplicity and clarity of illustration, elements illustrated in thefigures have not necessarily been drawn to scale. For example, thedimensions of some of the elements are exaggerated relative to otherelements. Embodiments incorporating teachings of the present disclosureare shown and described with respect to the figures presented herein, inwhich:

FIG. 1 illustrates a disassembled view of a material handling systemhaving a load frame that utilizes one or two hydraulic grip fixtures,according to one or more embodiments;

FIG. 2 illustrates a perspective view of the hydraulic grip fixture ofFIG. 1, according to one or more embodiments;

FIG. 3A is a partially cutaway detail view of a hydraulic grip wedge ofthe hydraulic grip fixture of FIG. 2, according to one or moreembodiments;

FIG. 3B is a detail view of a hydraulic grip wedge and cable clip of thehydraulic grip fixture of FIG. 2, according to one or more embodiments;

FIG. 4A is a perspective view of an example cable clip of FIG. 3B,according to one or more embodiments;

FIG. 4B is a top view of the example cable clip of FIG. 4A, according toone or more embodiments;

FIG. 4C is a side view of the example cable clip of FIG. 4A, accordingto one or more embodiments;

FIG. 4D is an end view of the example cable clip of FIG. 4A, accordingto one or more embodiments; and

FIG. 5 presents a flow diagram of a method of performing materialtesting with an improved hydraulic grip fixture, according to one ormore embodiments.

DETAILED DESCRIPTION

According to aspects of the present disclosure, a material testingsystem that uses at least one hydraulic grip fixture is improved withcable clips that are attachable to a respective lateral side of eachhydraulic grip wedge. Each cable clip has another end that extends toengage a cable extending from a corresponding wedge retention springhole. The cable enables manual extension of a wedge retention spring forengagement and disengagement from the hydraulic grip wedge. The cableclip maintains the cable in a noninterfering position during operationaluse of the material testing system.

In one or more embodiments, the present innovation provides a convenientmeans of keeping cables out of the way of fingers and hands while aperson is attempting to mount, un-mount or otherwise access a specimenbeing tested using the hydraulic wedge grips of a servohydraulic testmachine. Today, the common method of restraining these wires is to usecopious amounts of tape to tape the stiff wires out of the way. This issometimes ineffective as the wires come loose from the tape, and it awasteful use of tape.

FIG. 1 illustrates a disassembled view of a material handling system 100having a load frame 102 that utilizes one or two hydraulic grips 104attached respectively to upper and lower attachment fixtures 105 a-105b. One of the upper and lower attachment fixtures 105 a-105 b can omitgripping, such as using a pin and clevis system 106 attached to upperattachment fixture 105 a. The load frame 102 includes a base 108 havingsupport feet 109 positioned on a support surface 110. A pair of verticalcolumns 112 a-112 b extend upwardly from a base housing 113 of the base108. A crosshead 114 is received for vertical movement on the pair ofvertical columns 112 a-112 b and provides the upper attachment fixture105 a. The base housing 113 encloses and supports a main actuator 115that provides the lower attachment fixture 105 b. A pair of hydrauliclinear actuators 116 a-116 b attached between the base 108 and thecrosshead 114 to position the crosshead 114 for the length of a testspecimen 118. Crosshead 114 is then locked to vertical columns 112 a-112b. The hydraulic grip 104 receives one end of the test specimen 118 andthat is positioned between and attached to one of: (i) the base 108 andthe crosshead 114. The hydraulic grip 104 includes a fixture body 120having a wedge recess 122. A pair of hydraulic grip wedges 124 arereceived in opposition within the wedge recess 122. Each hydraulic gripwedge 124 are flexibly retained within the wedge recess 122 by wedgeretention springs 128 that are extended by cables 130. After theretention springs 128 are attached to a respective hydraulic grip wedge124, each cable 130 is held in positioned by a cable clip 132.

FIG. 2 illustrates a perspective view of the hydraulic grip 104. Eachhydraulic grip wedge 124 has a pair of vertical wedge retention springholes 126 out of which the cables 130 extend for manual extension of thewedge retention springs 128 (FIG. 1). The cables 130 are maintained in anoninterfering position by cable clips 132 that attach to a respectivelateral side 134 of one of the hydraulic grip wedges 124. In one or moreembodiments, the cable clips 132 engage spring retention bolts 134.

FIG. 3A is a partially cutaway detail view of a hydraulic grip wedge 124of the hydraulic grip 104. One vertical wedge retention spring hole 126is depicted in phantom. A wedge retention spring 128 is hooked to anattachment eye 136 mounted to a lower surface of the wedge recess 122 ofthe fixture body 120 of the hydraulic grip 104. A spring retention bolt138 is inserted through a horizontal spring retention hole 140 to engagea top end of the wedge retention spring 128. The cable 130 is engaged tothe other end respectively of each extension spring 128 and extends outof the corresponding hydraulic grip wedge 124, enabling manual extensionof the respective retention spring 128. In particular, the cable 130enables aligning the free end of the wedge retention spring 128 with thehorizontal spring retention hole 140 so that the spring retention bolt138 may be inserted.

FIG. 3B is a detail view of the hydraulic grip wedge 124 and the cableclip 132 of the hydraulic grip 104. The hydraulic grip wedge 124 isallowed by the wedge retention spring 128 to move in and out ofengagement with a test specimen 118 (FIG. 1). The cables 130 aremaintained in a noninterfering position by cable clips 132 that attachto a respective lateral side 134 of one of the hydraulic grip wedges124. The cable clips 132 are respectively attached at one end to alateral side 134 of one of the pair of hydraulic grip wedges 124 andengaged at another end to a corresponding cable 130 to maintain thecable 130 in a noninterfering position. In one or more embodiments, thecable clip 132 resembles a bent combination wrench with partially opensocket ends that end engaging to already installed bolt head 142 of thehorizontal spring retention bolt 138 (FIG. 3A) and cable 130.

FIG. 4A is a perspective view of an example cable clip 132. FIG. 4B is atop view of the example cable clip 132. FIG. 4C is a side view of theexample cable clip 132. FIG. 4D is an end view of the example cable clip132. In one or more embodiments, the new clips provide a reusable way torestrain these wires without using tape. The clip orientation can beadjusted, and the clip is reusable. The clips can be manufactured out ofpolymer material quickly using rapid prototyping (a 3D printer). Theclips can be flat and semi-rigid having a hole for retention by theexisting spring retention screw with an identical hole in the other endfor retaining the cable. Both holes have slots for sliding the cableinto the hole for retention. Both holes are slotted so that the clip canbe installed either with the slots toward the front or rear of themachine, which gives additional flexibility in the cable orientationonce retained. The clip is bent slightly in the middle, which retainsthe cable in a direction away from the specimen, and also improves easeof inserting the cable in the slot. The clip is easily installed by oneperson during wedge installation. Two clips are used for each wedge, andtherefore eight clips per installation (four for the two lower wedgesand four for the two upper wedges). The clip is easily fabricated, lightin weight, effective and very inexpensive.

In one or more embodiments, a cable clip 132 has two configurations:slots forward, slots aft. The configuration is easily changed anddepends upon where the cable is to be retained. A cable clip 132 couldbe machined from metal sheet (aluminum, steel, etc.), or, as has beendone to date, a cable clip 132 can be fabricated from polymer using arapid prototyping machine (3D printer). A cable clip 132 could be madefrom most any material sufficiently stiff to withstand handling, retainthe cable in place, and be resilient to withstanding the friction fromthe existing spring retention screw.

FIG. 5 presents a flow diagram of a method 500 of performing materialtesting with an improved hydraulic grip. The method 500 includesactuating a pair of hydraulic linear actuators that are attached betweena base of the load frame that support the main actuator and thecrosshead to position the crosshead to a selected vertical position on apair of vertical columns attached to the base (block 502). The selectedvertical position corresponds to a length of the test specimen. Method500 includes locking the crosshead to the pair of vertical columns atthe selected vertical position prior to actuating the main actuator tomaterially test the test specimen (block 504). The method 500 includesattaching a fixture body of a hydraulic grip to one of a lowerattachment fixture atop a main actuator and an upper fixture attached toa crosshead of a load frame (block 506). The method 500 includesattaching four wedge retention springs to a recess of the fixture body(block 508). The method 500 includes passing respective one or morecables attached to each wedge retention spring through a correspondingvertical wedge retention spring hole in one of a pair of hydraulic gripwedges (block 510). The method 500 includes, with a respective wedgeretention spring extended in the wedge retention spring hole by manualactuation of a corresponding cable to align the free end of the springwith the wedge retention spring hole, the method 500 includes insertinga retention spring retention bolt through the spring end via ahorizontal bolt hole that intersects the vertical wedge retention springhole (block 512). The method 500 includes attaching one end of a cableclip respectively to each lateral side of the pair of hydraulic gripwedges (block 514). The method 500 includes engaging another end of thecable clip to a corresponding cable to maintain the cable in anoninterfering position (block 516). The method 500 includes engaging atest specimen between the pair of hydraulic grip wedges (block 518). Themethod 500 includes actuating the main actuator to materially test thetest specimen (block 520). Then method 500 ends.

For clarity, the material testing system is described herein as movingin a vertical direction, reducing the required footprint and enhancingaccess to each side of the test specimen and equipment. In one or moreembodiments, aspects of the present innovation can be implemented in ahorizontally oriented material testing system.

While the disclosure has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular system,device or component thereof to the teachings of the disclosure withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the disclosure not be limited to the particular embodimentsdisclosed for carrying out this disclosure, but that the disclosure willinclude all embodiments falling within the scope of the appended claims.Moreover, the use of the terms first, second, etc. do not denote anyorder or importance, but rather the terms first, second, etc. are usedto distinguish one element from another.

In the preceding detailed description of exemplary embodiments of thedisclosure, specific exemplary embodiments in which the disclosure maybe practiced are described in sufficient detail to enable those skilledin the art to practice the disclosed embodiments. For example, specificdetails such as specific method orders, structures, elements, andconnections have been presented herein. However, it is to be understoodthat the specific details presented need not be utilized to practiceembodiments of the present disclosure. It is also to be understood thatother embodiments may be utilized and that logical, architectural,programmatic, mechanical, electrical and other changes may be madewithout departing from general scope of the disclosure. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present disclosure is defined by the appendedclaims and equivalents thereof.

References within the specification to “one embodiment,” “anembodiment,” “embodiments”, or “one or more embodiments” are intended toindicate that a particular feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present disclosure. The appearance of such phrases invarious places within the specification are not necessarily allreferring to the same embodiment, nor are separate or alternativeembodiments mutually exclusive of other embodiments. Further, variousfeatures are described which may be exhibited by some embodiments andnot by others. Similarly, various requirements are described which maybe requirements for some embodiments but not other embodiments.

It is understood that the use of specific component, device and/orparameter names and/or corresponding acronyms thereof, such as those ofthe executing utility, logic, and/or firmware described herein, are forexample only and not meant to imply any limitations on the describedembodiments. The embodiments may thus be described with differentnomenclature and/or terminology utilized to describe the components,devices, parameters, methods and/or functions herein, withoutlimitation. References to any specific protocol or proprietary name indescribing one or more elements, features or concepts of the embodimentsare provided solely as examples of one implementation, and suchreferences do not limit the extension of the claimed embodiments toembodiments in which different element, feature, protocol, or conceptnames are utilized. Thus, each term utilized herein is to be given itsbroadest interpretation given the context in which that terms isutilized.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope of the disclosure. Thedescribed embodiments were chosen and described in order to best explainthe principles of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A material testing system comprising: a load frame comprising: a base positioned on a support surface, a main actuator supported by the base and below a lower attachment fixture that is vertically actuated by the main actuator, and an upper fixture that is held at a distance from the lower attachment fixture; and at least one hydraulic grip that receives one end of a test specimen and that is positioned between and attached to one of: (i) the lower attachment fixture and the upper fixture and comprising: a fixture body having a wedge recess, a pair of hydraulic grip wedges received in opposition within the wedge recess, each hydraulic grip wedge having a pair of vertical wedge retention spring holes that are perpendicularly intersected respectively by a horizontal retention bolt hole, four retention springs having one end attached to the fixture body and another end extending upward respectively in the vertical wedge retention spring holes, a cable engaged to the other end respectively of each extension spring and extending out of the corresponding hydraulic grip wedge, enabling manual extension of the respective retention spring, at least two spring retention bolts received respectively in the horizontal retention bolt holes to attach to the other end of the wedge retention spring during extension by the corresponding cable, and four or more cable clips that are respectively attached at one end to a lateral side of one of the pair of hydraulic grip wedges and engaged at another end to a corresponding cable to maintain the cable in a noninterfering position.
 2. The material testing system of claim 1, wherein the load frame further comprises: a pair of vertical columns extending upwardly from the base, a crosshead received for vertical movement on the pair of vertical columns and lockable at a selected vertical position on the pair of vertical columns that corresponds to a length of the test specimen, and a pair of hydraulic linear actuators attached between the base and the crosshead to position the crosshead to the selected vertical position; and
 3. The material testing system of claim 1, wherein the four or more cable clips each comprise an elongate strip having an aperture at both ends, one aperture attachable by a fastener to the corresponding lateral side of the one of the pair of hydraulic grip wedges, vertically positioning a first portion into contact with the corresponding lateral side, another portion of each cable clip bent at an acute angle away from a plane of the corresponding lateral side.
 4. A method comprising: attaching a fixture body of a hydraulic grip to one of a lower attachment fixture atop a main actuator and an upper attachment fixture attached to a crosshead of a load frame; attaching four wedge retention springs to a recess of the fixture body; passing respective one or more cables attached to each wedge retention spring through a corresponding vertical wedge retention spring hole in one of a pair of hydraulic grip wedges; with a respective wedge retention spring extended in the wedge retention spring hole by manual actuation of a corresponding cable; inserting a retention spring retention bolt through a horizontal bolt hole that intersects the vertical wedge retention spring hole; attaching one end of a cable clip respectively to each lateral side of the pair of hydraulic grip wedges; engaging another end of the cable clip to a corresponding cable to maintain the cable in a noninterfering position; engaging a test specimen between the pair of hydraulic grip wedges; and actuating the main actuator to materially test the test specimen.
 5. The method of claim 4, further comprising: actuating a pair of hydraulic linear actuators that are attached between a base of the load frame that support the main actuator and the crosshead to position the crosshead to a selected vertical position on a pair of vertical columns attached to the base, the selected vertical position corresponding to a length of the test specimen; and locking the crosshead to the pair of vertical columns at the selected vertical position prior to actuating the main actuator to materially test the test specimen. 